• Srinivas Pandruvada's avatar
    cpufreq: intel_pstate: Fix scaling max/min limits with Turbo 3.0 · ff7c9917
    Srinivas Pandruvada authored
    When scaling max/min settings are changed, internally they are converted
    to a ratio using the max turbo 1 core turbo frequency. This works fine
    when 1 core max is same irrespective of the core. But under Turbo 3.0,
    this will not be the case. For example:
    Core 0: max turbo pstate: 43 (4.3GHz)
    Core 1: max turbo pstate: 45 (4.5GHz)
    In this case 1 core turbo ratio will be maximum of all, so it will be
    45 (4.5GHz). Suppose scaling max is set to 4GHz (ratio 40) for all cores
    ,then on core one it will be
     = max_state * policy->max / max_freq;
     = 43 * (4000000/4500000) = 38 (3.8GHz)
     = 38
    which is 200MHz less than the desired.
    On core2, it will be correctly set to ratio 40 (4GHz). Same holds true
    for scaling min frequency limit. So this requires usage of correct turbo
    max frequency for core one, which in this case is 4.3GHz. So we need to
    adjust per CPU cpu->pstate.turbo_freq using the maximum HWP ratio of that
    core.
    
    This change uses the HWP capability of a core to adjust max turbo
    frequency. But since Broadwell HWP doesn't use ratios in the HWP
    capabilities, we have to use legacy max 1 core turbo ratio. This is not
    a problem as the HWP capabilities don't differ among cores in Broadwell.
    We need to check for non Broadwell CPU model for applying this change,
    though.
    Signed-off-by: default avatarSrinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
    Cc: 4.6+ <stable@vger.kernel.org> # 4.6+
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    ff7c9917
intel_pstate.c 64 KB